1. Field of the Invention
This invention relates to an image forming apparatus, more particularly to an image forming apparatus, which can form a toner image by an electrostatic copying process based on image data sent supplied from an outer unit, and output the image on sheet material.
2. Description of the Related Art
The image forming apparatus such as a laser beam printer receives image data from an outer unit such as a host computer or a wordprocessor, develops received data to bit image data, and prints out an image on sheet. However, in order to add data excepting characters, marks, or figures included in image data, such as a central mark showing a center of sheet, data must be directly added to image data itself supplied from a host computer.
In other words, in the case that an image to be printed is supplied from the wordprocessor, it is required that the central mark be added to image data stored in the wordprocessor. Similarly, in the case that image data is supplied from the host computer, the central mark cannot be added to image data if the central mark is not passed through the host computer.
As mentioned above, data to be added to image data such as the central mark showing the center of sheet must be newly inputted through the image data forming apparatus or image data supplying apparatus.
Since image data, which is already completed, must be newly remade in order to newly input data to be added, a large amount of time is required. Also, in the case that the host computer is provided at a remote place, there is substantial difficulty in that data to be immediately added is incorporated to image data once transmitted. On the other hand, remaking image data, which is already completed, must be avoided since there is a possibility that erroneous data will be newly inputted.